Comparative fundamentality and levels of reality

Abstract Much philosophy presupposes a picture of reality as stratified into levels or layers. Yet a precise articulation of such a picture has been missing. It is tempting to think that we now have the tools to remedy this, notably due to ground-theoretic accounts of relative fundamentality. One might expect levels of facts, and their hierarchical arrangement, to be definable from relative fundamentality among facts. I show that such a project can at best partially succeed, by establishing certain limitative results. Moreover, I argue that the limitations should not be surprising, in light of an analogy between levels of reality and instants of time. Facts may exist at more than one level, just like persisting objects exist at more than one time. Finally, I develop a new positive proposal, on which levels are not made up of facts, but of what I call “fact realisations”—roughly, facts together with a complete genealogy of their grounds.